I think if you read between the lines of the story so far, the writers are building up to season 13 being a wrap up season. Little details like the carving of their names into the bunker table, which hearkens back to the same thing they did as children in the Impala, arguably bringing Mary Winchester back into the fray, the nod to JDM with 'Lucille' earlier in the season, the re-entrance of the colt and the link between John, Mary and Azazel, Sam's demon blood etc. More overtly, Dean and Sam pondering on their legacy. There will be a lot of loose ends to tie off, and just shy of 30 episodes in which to do it. Personally, I think it would be great if somehow Lucifer's baby was integral to the whole thing. It would be tedious to have a re- enactment of the whole Amara's accelerated development phase again, I think they should strive for something different. If it is morally wrong for the Nephilim to be killed as a baby, perhaps Sam, Dean, Mary, Crowley and Castiel could attempt to co-opt it over to the good side. (Difficult for Crowley to do admittedly, but he could still play some role). It might initially require the intervention of God and his sister Amara in some way, but then the main cast could cooperate to mould the Nephilim into an ethical being, along the lines of Kevin Lomax in DA. If his phenomenal power is primarily psychic, it would make for more nuanced plot lines and less special effects than were required with Amara.
On a side note, before the show ends production for good, maybe they could devote an episode or two to American politics and the batsh*t crazy stuff that went on at Bohemian Grove, as well as examining the Kennedys in some way. It would be a very difficult sell, given the public affection for that family. I don't know if BG and the Kennedys are related, but that would have to be ascertained. If doing so, perhaps wisest to leave it towards the end of S13, if at all. There is a lot of occultism that occurred there, some pretty sordid stuff. Whatever the incumbent C-i-C's faults are, and they are manifold, that type of w*nk is not one of them - in fact, the BG cabal conspired to elect HRC, and in thereby doing, their agenda failed massively.